✧ First-author Works
Piacitelli et al. 2025
Marvelous Metals: Surveying the Circumgalactic Medium of Simulated Dwarf Galaxies
Abstract:
Dwarf galaxies are uniquely sensitive to energetic feedback processes and are known to experience substantial mass and metal loss from their disk. Here, we investigate the circumgalactic medium (CGM) of 64 isolated dwarf galaxies (6.0 < log(M∗/M⊙) < 9.5) at z = 0 from the Marvel-ous Dwarfs and Marvelous Massive Dwarfs hydrodynamic simulations. Our galaxies produce column densities broadly consistent with current observations. We investigate these column densities in the context of mass and metal retention rates and the physical properties of the CGM. We find 48 ± 11% of all baryons within R200c reside in the CGM, with ∼ 70% of CGM mass existing in a warm gas phase, 4.5 < logT/K < 5.5 that dominates beyond r/R200c ∼ 0.5. Further, the warm and cool (4.0 < logT/K < 4.5) gas phases each retain 5 − 10% of metals formed by the dwarf galaxy. The significant fraction of mass and metals residing in the warm CGM phase provides an interpretation for the lack of observed low ion detections beyond b/R200c ∼ 0.5 at z ∼ 0, as the majority of mass in this region exists in higher ions. We find a weak correlation between galaxy mass and total CGM metal retention despite the fraction of metals lost from the halo increasing from ∼ 10% to > 40% towards lower masses. Our findings highlight the CGM (primarily its warm component) as a key reservoir of mass and metals for dwarf galaxies across stellar masses and underscore its importance in understanding the baryon cycle in the low-mass regime. Finally, we provide individual galaxy properties of our full sample and quantify the fraction of ultraviolet observable mass to support future observational programs, particularly those aimed at performing a metal budget around dwarf galaxies.
Piacitelli & Solhaug et al. 2022 (co-lead author)
Absorption-based circumgalactic medium line emission estimates
Abstract:
Motivated by integral field units (IFUs) on large ground telescopes and proposals for ultraviolet-sensitive space telescopes to probe circumgalactic medium (CGM) emission, we survey the most promising emission lines and how such observations can inform our understanding of the CGM and its relation to galaxy formation. We tie our emission estimates to both HST/COS absorption measurements of ions around z ≈ 0.2 Milky Way mass haloes and models for the density and temperature of gas. We also provide formulas that simplify extending our estimates to other samples and physical scenarios. We find that O III 5007 Å and N II 6583 Å, which at fixed ionic column density are primarily sensitive to the thermal pressure of the gas they inhabit, may be detectable with KCWI and especially IFUs on 30 m telescopes out to half a virial radius. O V 630 Å and O VI 1032,1038 Å are perhaps the most promising ultraviolet lines, with models predicting intensities >100 γ cm−2 s−1 sr−1 in the inner 100 kpc of Milky Way-like systems. A detection of O VI would confirm the collisionally ionized picture and constrain the density profile of the CGM. Other ultraviolet metal lines constrain the amount of gas that is actively cooling and mixing. We find that C III 978 Å and C IV 1548 Å may be detectable if an appreciable fraction of the observed O VI column is associated with mixing or cooling gas. H α emission within 100 kpc of Milky Way-like galaxies is within reach of current IFUs even for the minimum signal from ionizing background fluorescence, while hydrogen n > 2 Ly-series lines are too weak to be detectable.
✧ Co-author Works
Here, I highlight past works I have contributed to as a co-author:
Signatures of Density Fluctuations in CGM Absorption (2024)
In my final quarter at the University of Washington, I worked with Post-Doc Yakov Faerman and Professor Matt McQuinn to better understand the effect of variations in temperature and density along a sightline on the inferred gas properties from observations. This research is pertinent for CGM research as models for photoionization are used to translate ion column densities measured from absorption lines to the density and ionization state of the absorbing gas. While these models have greatly informed our perspective of the CGM, they often rely on assuming the absorbing gas exists at a single temperature and density, which does not account for the effects of turbulent or mixing gas. Thus, more realistic photoionization models are required to better constrain CGM properties. For this project, I used models of gas density and temperature to explore physical scenarios likely to be present in the CGM, for instance, gas that is mixing, turbulent, or cooling. I then used Cloudy to calculate the ion abundances for each scenario and compared our results to observations to understand the effect of these distributions.
The Impact of Cosmic Rays on the Kinematics of the CGM (2022)
As an undergraduate at the University of Washington working with Graduate Student Iryna Butsky, I contributed to this project by utilizing novel synthetic spectroscopy techniques to determine column densities and velocity distributions of various ions within the Patient0 galaxy simulation and a second Patient0 iteration with CR physics implemented. Extracting this data using Python-based, observer-developed Voigt profile fitting tools, I was able to directly compare spectral line properties in our simulation to observations in the COS-Halos survey. With this approach, we demonstrated the implementation of CRs produced O VI and Si III kinematic structures and absorption feature widths in better agreement with observations.
Butsky, I. S., Werk, J. K., Tchernyshyov, K., Fielding, D., Breneman, J., Piacitelli, D. R., Quinn, T., Sanchez, N., Cruz, A., Hummels, C., et al. 2022